Thermally enhanced light emitting device package

ABSTRACT

A thermally enhanced light emitting device package includes a substrate, a chip attached to the substrate, an encapsulant overlaid on the chip, and a plurality of non-electrically conductive carbon nanocapsules mixed in the encapsulant to facilitate heat dissipation from the chip.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting device package, andrelates more particularly to a thermally enhanced light emitting devicepackage.

2. Description of the Related Art

Due to their low power consumption and high illumination efficiency,LEDs are increasingly adopted in many electronic devices such as mobiledevices, advertising light boxes, screens, signal lights, automotivevehicle signal lights, etc. As is well known, LEDs generate asignificant amount of heat when they emit light, and heat sinks arenecessary to dissipate the generated heat.

An LED package is primarily constituted by a heat sink, an LED disposedon the heat sink, and an encapsulant covering the LED. Light from theLED is emitted externally through the encapsulant. Because theencapsulant is usually made of polymer having poor thermal conductivity,most of the generated heat is dissipated through the heat sink.

To attain high illumination levels, high power LEDs are necessary. Highpower LEDs generate more heat that cannot be sufficiently dissipated byheat sinks. Therefore, complex heat dissipation designs are required,increasing the volume, weight, and cost of LED packages.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a thermally enhancedlight emitting device package, which comprises a leadframe, a chip, aplurality of metal wires, an encapsulant, and a plurality ofnon-electrically conductive carbon nanocapsules. The chip is attached tothe leadframe. The metal wires electrically connect the chip and theleadframe. The plurality of non-electrically conductive carbonnanocapsules are mixed in the encapsulant where the encapsulantencapsulates the leadframe, the chip, and the metal wires.

Another embodiment of the present invention provides a thermallyenhanced light emitting device package, which comprises a substrate, achip, an encapsulant, and a plurality of non-electrically conductivecarbon nanocapsules where a plurality of bumps are disposed on the bondpads of the chip. The chip is a flip chip disposed on the substrate. Theplurality of non-electrically conductive carbon nanocapsules are mixedin the encapsulant where the encapsulant encapsulates at least part ofthe substrate, the chip, and the bumps.

Another embodiment of the present invention provides a thermally isenhanced light emitting device package, which comprises a substrate, achip, an encapsulant, a plurality of metal wires electrically connectingthe chip and the substrate, a plurality of metal wires, a lens, andanother plurality of non-electrically conductive carbon nanocapsulesmixed in the lens where the encapsulant encapsulates at least part ofthe substrate, the chip, and the metal wires.

To better understand the above-described objectives, characteristics andadvantages of the present invention, embodiments, with reference to thedrawings, are provided for detailed explanations.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described according to the appended drawings inwhich:

FIG. 1 is a cross-sectional view illustrating a thermally enhanced lightemitting device package according to a first embodiment of the presentinvention;

FIG. 2 is a cross-sectional view illustrating a thermally enhanced lightemitting device package according to a second embodiment of the presentinvention;

FIG. 3 is a cross-sectional view illustrating a thermally enhanced lightemitting device package according to a third embodiment of the presentinvention;

FIG. 4 is a cross-sectional view illustrating a thermally enhanced lightemitting device package according to a fourth embodiment of the presentinvention;

FIG. 5 is a cross-sectional view illustrating a thermally enhanced lightemitting device package according to a fifth embodiment of the presentinvention;

FIG. 6 is a cross-sectional view illustrating a thermally enhanced lightemitting device package according to a sixth embodiment of the presentinvention;

FIG. 7 is a cross-sectional view illustrating a thermally enhanced lightemitting device package according to a seventh embodiment of the presentinvention; and

FIG. 8 is a cross-sectional view illustrating a thermally enhanced lightemitting device package according to an eighth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a cross-sectional view illustrating a thermally enhanced lightemitting device package 10 according to a first embodiment of thepresent invention. FIG. 2 is a cross-sectional view illustrating athermally enhanced light emitting device package 20 according to asecond embodiment of the present invention. Referring to FIGS. 1 and 2,the thermally enhanced light emitting device package 10 or 20 comprisesa leadframe 13, a chip 12 attached to the leadframe 13, a plurality ofmetal wires 15 electrically connecting the chip 12 and the leadframe 13,an encapsulant 14 mixed with a plurality of non-electrically conductivecarbon nanocapsules 16 and encapsulating the chip 12, the leadframe 13,and the metal wires 15.

As shown in FIG. 1, the thermally enhanced light emitting device package10 may further comprise a fluorescent adhesive 11 overlaid on the chip12, converting a portion of light from the chip 12 into complementarycolor light combined with another portion of light from the chip 12 tosimulate white light.

In one embodiment, the fluorescent adhesive 11 can be mixed with aplurality of non-electrically conductive carbon nanocapsules 16.

As shown in FIGS. 1 and 2, the leadframe 13 may include a cathode 13 aand an anode 13 b. As is well known, the chip 12 is comprised of issemiconducting material doped with impurities to create a p-n junction.Current flows from the anode 13 b or p-side to the cathode 13 a orn-side, and when an electron collides with a hole, energy is released inthe form of a photon, i.e., light. Therefore, when electrons continue tocollide with holes, light will emit continuously.

Referring to FIGS. 1 and 2 again, the leadframe 13 may further comprisea downset 13 c, in which the chip 12 is disposed. The fluorescentadhesive 11 is disposed in the downset 13 c to encapsulate the chip.

The encapsulant 14 can be formed to encapsulate the end portion of thecathode 13 a, the end portion of the anode 13 b, the downset 13 c, andthe chip 12 in the embodiment of FIG. 1, and is formed to furtherencapsulate the fluorescent adhesive 11 in the embodiment of FIG. 2. Theencapsulant 14 can further be formed to include a lens part 141 forfocusing emitted light to enhance light intensity and to control lightemitting directions. The encapsulant 14 is comprised of dielectric resinmaterial. In one embodiment, the encapsulant 14 can be comprised ofthermosetting polymer such as silicone, epoxy resin, urethane, acrylics,or the like. In an alternative embodiment, the encapsulant 14 can becomprised of a thermoplastic material such as polyethylene,polypropylene, polycarbonate, polyethylene terephthalate, polyacrylate,acrylonitrile-styrene-butadiene copolymer, or the like.

As illustrated in FIGS. 1 and 2, the thermally enhanced light emittingdevice package 10 or 20 includes a plurality of non-electricallyconductive carbon nanocapsules 16 distributed in the encapsulant 14 suchthat a heat dissipating path is formed inside the encapsulant 14. Theplurality of non-electrically conductive carbon nanocapsules 16 canfacilitate the dissipation of heat from the chip 12. Specifically, theplurality of non-electrically conductive carbon nanocapsules 16 canabsorb the heat from the chip 12 and dissipate it in the form ofinfrared radiation.

In one embodiment, the surfaces of the carbon nanocapsules 16 can befunctionalized to achieve good interfacial adhesion between the carbonnanocapsules 16 and the encapsulant 14.

The carbon nanocapsules 16 can effectively dissipate heat from the chip12; thus a low loading of carbon nanocapsules 16 is sufficient for heatdissipation purpose. In one embodiment, 10% or less, preferably 1%, byweight of carbon nanocapsules 16 is blended into the encapsulant 14 andsuch a low loading will not compromise the light transmission throughthe encapsulant 14.

FIG. 3 is a cross-sectional view illustrating a thermally enhanced lightemitting device package 30 according to a third embodiment of thepresent invention. Referring to FIG. 3, the thermally enhanced lightemitting device package 30 comprises a substrate 33, a chip 32 attachedto the substrate 33, a plurality of metal wires 35 electricallyconnecting the chip 32 and the substrate 33, an encapsulant 34 mixedwith a plurality of non-electrically conductive carbon nanocapsules 16and encapsulating the chip 32, the substrate 33 and a plurality of metalwires 35.

As shown in FIG. 3, the substrate 33 may include a cathode 33 a, ananode 33 b, and a support portion 33 c. Each of the cathode 33 a and theanode 33 b is formed on the support portion 33 c, extending along andfrom one surface of the support portion 33 c, around a correspondingsidewall, to and along an opposite surface. In one embodiment, the chip32 is disposed on the cathode 33 a. The substrate 33 may be a printedcircuit board such as FR-4, FR-5, BT, or the like, a metal-core printedcircuit board, a ceramic substrate, a flex film, or the like.

The encapsulant 34 mixed with the plurality of non-electricallyconductive carbon nanocapsules 16 is disposed on top of the substrate 33and encapsulates the chip 32 and the wires 35 for dissipating heatgenerated by the chip 32. Similar to the above embodiment, 10% or less,preferably 1%, by weight of carbon nanocapsules 16 is sufficient forheat dissipation is purpose. The encapsulant 34 is comprised ofdielectric resin material. In one embodiment, the encapsulant 34 can becomprised of thermosetting polymer such as silicone, epoxy resin,urethane, acrylics, or the like. In another embodiment, the encapsulant34 can be comprised of a thermoplastic material such as polyethylene,polypropylene, polycarbonate, polyethylene terephthalate, polyacrylate,acrylonitrile-styrene-butadiene copolymer, or the like.

FIG. 4 is a sectional view showing a thermally enhanced light emittingdevice package 40 according to a fourth embodiment of the presentinvention. Referring to FIG. 4, the thermally enhanced light emittingdevice package 40 comprises a substrate 33, a chip 32 attached to thesubstrate 33, a plurality of metal wires 35 electrically connecting thechip 32 and the substrate 33, an encapsulant 44 encapsulating the chip32 and the top surface of the substrate 33, and a plurality ofnon-electrically conductive carbon nanocapsules 16 mixed in theencapsulant 44.

The substrate 33 is analogous to that of the embodiment of FIG. 3,including an anode 33 b and a cathode 33 a, to which the chip 32 isattached.

As shown in FIG. 4, the thermally enhanced light emitting device package40 comprises a reflector 47 formed on the substrate 33 for reflectingthe light emitted from the chip 32 in the desired direction. Thereflector 47 can be an additional component attached to the peripheriesof the substrate 33 before encapsulation or part of the substrate 33 tobe filled with encapsulant 44.

The encapsulant 44 can encapsulate the chip 32 and the wires 35. Theencapsulant 44 is comprised of dielectric resin material. In oneembodiment, the encapsulant 44 can be comprised of thermosetting polymersuch as silicone, epoxy resin, urethane, acrylics, or the like. Inanother embodiment, the encapsulant 44 can alternatively be comprised ofa thermoplastic material such as polyethylene, polypropylene,polycarbonate, polyethylene terephthalate, polyacrylate,acrylonitrile-styrene-butadiene is copolymer, or the like. Theencapsulant 44 can be mixed with 10% or less, preferably 1%, by weightof carbon nanocapsules 16 for dissipating heat from the chip 32.

In FIG. 4, the thermally enhanced light emitting device package 40 mayfurther comprise a lens 48 disposed on the encapsulant 44 for directinglight in the desired direction. The lens 48 can include 10% or less byweight of carbon nanocapsules 16 so that a heat dissipating path can beformed therein. The lens 48 can be comprised of thermosetting polymersuch as silicone, epoxy resin, urethane, acrylics, or the like, or canalternatively be comprised of a thermoplastic material such aspolyethylene, polypropylene, polycarbonate, polyethylene terephthalate,polyacrylate, acrylonitrile-styrene-butadiene copolymer, or the like.

FIG. 5 is a cross-sectional view illustrating a thermally enhanced lightemitting device package 50 according to a fifth embodiment of thepresent invention. Referring to FIG. 5, the thermally enhanced lightemitting device package 50 comprises a substrate 53, a chip 52, aplurality of metal wires 55 electrically connecting the substrate 53 andthe chip 52, an encapsulant 54 encapsulating the chip 52, and aplurality of non-electrically conductive carbon nanocapsules 16.

As shown in FIG. 5, the substrate 53 can be a printed circuit boardhaving an opening. A thermal dissipation element 51 may be furtherprovided in the thermally enhanced light emitting device package 50,inserted in the opening of the substrate 53, with the chip 52 disposedon the thermal dissipation element 51. The thermal dissipation element51 can be made of, for example, metal.

The encapsulant 54 encapsulates the chip 52 and the metal wires 55. Aplurality of non-electrically conductive carbon nanocapsules 16 aremixed in the encapsulant 54 so that heat generated by the chip 52 caneffectively dissipate through the encapsulant 54 by thermal radiation.In one embodiment, 10% or less, preferably 1%, by weight of carbonnanocapsules is 16 are mixed in the encapsulant 54.

As shown in FIG. 5, an electrically insulating material 59 is furtherprovided to cover the exposed surface of the thermal dissipation element51 for electrical insulation. A plurality of non-electrically conductivecarbon nanocapsules 16 may be contained in the electrically insulatingmaterial 59 so as to allow the heat generated by the chip 52 todissipate effectively through the electrically insulating material 59.The electrically insulating material 59 can be comprised of athermosetting polymer such as silicone, epoxy resin, urethane, oracrylics, or of a thermoplastic material such as polyethylene,polypropylene, polycarbonate, polyethylene terephthalate, polyacrylate,acrylonitrile-styrene-butadiene copolymer. In one embodiment, 10% orless, preferably 1%, by weight of carbon nanocapsules 16 are mixed inthe electrically insulating material 59 based on the total amount of themixture of the electrically insulating material 59 and the carbonnanocapsules 16.

Referring to FIG. 5 again, the thermally enhanced light emitting devicepackage 50 may further comprise a lens 58 disposed on the encapsulant 54for directing light in the desired direction. The lens 58 can becomprised of thermosetting polymer such as silicone, epoxy resin,urethane, or acrylics, or of a thermoplastic material such aspolyethylene, polypropylene, polycarbonate, polyethylene terephthalate,polyacrylate, or acrylonitrile-styrene-butadiene copolymer.

As shown in FIG. 5, the thermally enhanced light emitting device package50 further comprises a reflector 57 disposed at the peripheries of theencapsulant 54 for reflecting light to increase light intensity and alens 58 for directing light in the desired direction.

FIG. 6 is a cross-sectional view illustrating a thermally enhanced lightemitting device package 60 according to a sixth embodiment of thepresent invention. Referring to FIG. 6, the thermally enhanced lightemitting device package 60 comprises a substrate 33 including a cathode33 a and an is anode 33 b, a chip 32 flip-chip bonded to the cathode 33a and the anode 33 b, an encapsulant 34 overlaid on the chip 32, and aplurality of non-electrically conductive carbon nanocapsules 16 mixedwith the encapsulant 34.

As shown in FIG. 6, the thermally enhanced light emitting device package60 may further comprise fluorescent powder mixed in the encapsulant 34to allow the thermally enhanced light emitting device package 60 tosimulate white light. The encapsulant 34 is mixed with the plurality ofnon-electrically conductive carbon nanocapsules 16 so that the heat fromthe chip 32 can effectively dissipate through the encapsulant 34. Theencapsulant 34 can be shaped like a sphere or a partial sphere fordirecting light in the desired direction.

The thermally enhanced light emitting device package 60 may furthercomprise an optical element 62 formed at the peripheries of theencapsulant 34 for protection and a reflection layer 61 formed betweenthe optical element 62 and the encapsulant 34 for reflecting the lightfrom the chip 32 to increase light intensity.

FIG. 7 is a cross-sectional view illustrating a thermally enhanced lightemitting device package 70 according to a seventh embodiment of thepresent invention. Referring to FIG. 7, the thermally enhanced lightemitting device package 70 comprises a plurality of contacts 71, athermal dissipation element 72 disposed between the plurality ofcontacts 71, a substrate 73 including a patterned metal layer 731, apatterned electrically conductive adhesive layer 74 electricallyconnecting the plurality of contacts 71 and the metal layer 731, a chip75 flip-chip bonded to the metal layer 731 and thermally coupled to thethermal dissipation element 72, an encapsulant 76 encapsulating the chip75, and a plurality of non-electrically conductive carbon nanocapsules16 dispersed in the encapsulant 76 to allow heat generated by the chip75 to effectively dissipate through the encapsulant 76.

The thermal dissipation element 72 can be made of thermally isconductive material such as copper, aluminum, or the like.

The electrically conductive adhesive layer 74 can be comprised of soldermaterial, silver paste, anisotropic conductive film, or the like.

The substrate 73 may further comprise two dielectric layers 732, whereinthe metal layer 731 is disposed between the two dielectric layers 732.

The thermally enhanced light emitting device package 70 may comprisefluorescent powder mixed in the encapsulant 76 to allow the thermallyenhanced light emitting device package 70 to simulate white light.

The thermally enhanced light emitting device package 70 furthercomprises an adhesive layer 77 formed between the chip 75 and thethermal dissipation element 72. The adhesive layer 77 bonds the chip 75and the thermal dissipation element 72 together, and electricallyinsulates the chip 75 from the thermal dissipation element 72. Theadhesive layer 77 may contain a plurality of non-electrically conductivecarbon nanocapsules 16 so that the heat generated by the chip 75 caneffectively dissipate through the adhesive layer 77.

FIG. 8 is a cross-sectional view illustrating a thermally enhanced lightemitting device package 80 according to an eighth embodiment of thepresent invention. Referring to FIG. 8, the thermally enhanced lightemitting device package 80 is similar to the thermally enhanced lightemitting device package 70 in FIG. 7, while the thermally enhanced lightemitting device package 80 further comprises a protection layer 82having an opening having a shape of a truncated cone, a reflection layer81 formed on the surface defining the opening, and the encapsulant 76included in the thermally enhanced light emitting device package 80contained in the reflection layer 81 and having a curved concavesurface. Similarly, a plurality of non-electrically conductive carbonnanocapsules 16 are dispersed in the encapsulant 76 and the adhesivelayer 77 to allow heat is generated by the chip 75 to effectivelydissipate through the encapsulant 76 and the adhesive layer 77.

The above-described embodiments of the present invention are intended tobe illustrative only. Numerous alternative embodiments may be devised bypersons skilled in the art without departing from the scope of thefollowing claims.

1. A thermally enhanced light emitting device package, comprising: aleadframe; a chip attached to the leadframe; a plurality of metal wireselectrically connecting the chip and the leadframe; a plurality ofnon-electrically conductive carbon nanocapsules; and an encapsulantmixed with the non-electrically conductive carbon nanocapsules,encapsulating the leadframe, the chip and the metal wires.
 2. Thethermally enhanced light emitting device package of claim 1, furthercomprising a fluorescent adhesive overlaid on the chip.
 3. The thermallyenhanced light emitting device package of claim 2, wherein thefluorescent adhesive is mixed with the non-electrically is conductivecarbon nanocapsules.
 4. The thermally enhanced light emitting devicepackage of claim 1, wherein the leadframe includes a downset in whichthe chip is mounted.
 5. The thermally enhanced light emitting devicepackage of claim 1, wherein the encapsulant has a lens part.
 6. Thethermally enhanced light emitting device package of claim 1, wherein theweight percentage of the non-electrically conductive carbon nanocapsulesblended into the encapsulant is less than 10%.
 7. A thermally enhancedlight emitting device package, comprising: a substrate; a chip attachedto the substrate; a plurality of non-electrically conductive carbonnanocapsules; and an encapsulant mixed with the plurality ofnon-electrically conductive carbon nanocapsules encapsulating at leastpart of the substrate and the chip.
 8. The thermally enhanced lightemitting device package of claim 7, further comprising a plurality ofmetal wires electrically connecting the chip and the substrate.
 9. Thethermally enhanced light emitting device package of claim 7, wherein thechip is flip-chip bonded to the substrate.
 10. The thermally enhancedlight emitting device package of claim 7, further comprising a thermaldissipation element thermally coupled to the chip.
 11. The thermallyenhanced light emitting device package of claim 10, further comprisingan electrically insulating material mixed with non-electricallyconductive carbon nanocapsules, covering the thermal dissipationelement.
 12. The thermally enhanced light emitting device package ofclaim 11, wherein the weight percentage of the non-electricallyconductive carbon nanocapsules blended into the electrical insulatingmaterial is less than 10%.
 13. The thermally enhanced light emittingdevice package of claim 10, further comprising an adhesive layer bondingthe chip and the thermal dissipation element, and another plurality ofnon-electrically conductive carbon nanocapsules mixed in the adhesivelayer.
 14. The thermally enhanced light emitting device package of claim13, wherein the weight percentage of the another plurality ofnon-electrically conductive carbon nanocapsules blended into theadhesive layer is less than 10%.
 15. The thermally enhanced lightemitting device package of claim 7, further comprising a lens disposedon the encapsulant.
 16. The thermally enhanced light emitting devicepackage of claim 7, wherein the weight percentage of thenon-electrically conductive carbon nanocapsules blended into theencapsulant is less than 10%.
 17. The thermally enhanced light emittingdevice package of claim 7, further comprising a reflector surroundingthe encapsulant.
 18. The thermally enhanced light emitting devicepackage of claim 7, further comprising an adhesive layer formed aroundthe encapsulant and a reflection layer formed between the adhesive layerand is the encapsulant.
 19. A thermally enhanced light emitting devicepackage, comprising: a substrate; a chip attached to the substrate; aplurality of metal wires electrically connecting the chip and thesubstrate; an encapsulant mixed with a plurality of non-electricallyconductive carbon nanocapsules, encapsulating at least part of thesubstrate, the wires and the chip; a lens disposed on the encapsulant;and another plurality of non-electrically conductive carbon nanocapsulesmixed in the lens.
 20. The thermally enhanced light emitting devicepackage of claim 19, wherein the weight percentage of thenon-electrically conductive carbon nanocapsules blended into theencapsulant is less than 10%.
 21. The thermally enhanced light emittingdevice package of claim 19, further comprising a reflector surroundingthe encapsulant.